Ferrous alloys for high temperature use



United States PatentOfi 1 2,801,916 Patented Aug. 6, 1957 ice,

No Drawing. Application August 24, 1954, Serial No. 451,965

6 Claims. (Cl. 75128) This invention relates to alloys intended for use in the production of articles which in use are subjected to high temperatures.

According to this invention alloys comprise:

Nickel and cobalt together shall not exceed 45%, The total of tungsten, molybdenum, niobium, tantalum,

one or all of the following more restricted ranges may be substituted for those given above:

Percent Carbon 0.15-0.45 Manganese 0.5-1.5 Silicon 0.15-0.75 Chromium 15-23 Nickel 13-28 Cobalt 1 22-28 Boron 0.002-0.04 Tungsten 0.5-3.5 Molybdenum 0.5-3.5 Niobium 0.5-3.5 Tantalum (1.5-3.5 Titanium 0.5-3.5 Vanadium 0.5-3.5

1 (Or alternatively 0-3 In the above mentioned ranges the amount of iron present is preferably less than A feature of the invention is that alloys according to the invention are particularly suitable for warm working, that is to say, working at temperatures between about 500 C. and 900 C., to give a reduction in thickness of up to about 20%. A surprising result of warm working is that the rupture-time at a given stress and temperature is significantly raised. Warm working as is usually the case, preferably follows solution heat treatment. Solutionheat treatment usually involves a treatment in which a steel is heated to a uniform temperature above 0 about 1000 C. and is maintained at that temperature for a suitable period of time.

Examples of alloys, in which the amounts are given by weight percent, according to the invention are:

Alloy L. 641 L. 729 L. 915 L. 1299 L. 908 L. 899 L. 1293 0. 4 0.4 0.25 0. 25 0.2 0. 20 0. 20 0.8 0.8 0.8 1.0 1.0 1.0 1.0 0. 5 0.5 0.3 0.3 0.3 0.3 0.5 15.0 15.0 15. 0 15.0 25. 0 25.0 25.0 25. 0 25. 0 25. 0 25.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 2.5 2.5 2.2 3.0 1.0 2.0 1.5 2.0 2.0 2.3 3.0 3.0 3.0 2.6 3.0 3.0 2.2 2.0 2.0 2. 3 1. 0 0. 03 0. 03 0. 03 0. 03 0. 03 1.0 2.0 Iron and Im- I purities Balance Balance Balance Balance Balance Balance Balance titanium, vanadium being between 5% and 10% and at least two of these elements being present.

According to a further feature of the invention any The following table shows properties of these alloys and the very substantial gains in creep and rupture properties resulting from warm working.

Time in Minimum Elong- Stress Temperhours to Creep ation, Material Tons] ature, 0. give 1% Fracture rate per percent sq. in. elonga-g h1'. 10- at fracture tlon L. 10 800 l, 3. 2 17 L. 10 800 1, 120 3, 117 0. 1 10 L. 16 750 10 225 31 14 L. 16 750 310 1, 298 l 10 L. 19 750 372 372 1. 0 1. 0 L. 14 800 195 501 1. 5 2. 0 L. 9 870 263 1. 5 2. 9

l 011 quenched 1280 O.

i 011 quenched 1280 0. Warm worked at 700 0., to give 5 to 107. reduction in thickness Generally speaking increased additions of cobalt in alloys of the kind herein specified result in increased creep strength. However, the use of boron materially assists in reducing the necessary quantity of cobalt. For instance in alloys of :li'llS general type, but without boron, the stress in tons per square inch for 300 hour rupture at 750 C., was about 13 with a proportion of 10% cobalt and this increased, more or less linearly, to about 19 with cobalt gradually increased to about 60%. When a proportion of 0.03% boron and cobalt was present the stress was 18 tons per square inch and this increased substantially linearly with increased quantities of cobalt to about 20.5 tons per square inch with cobalt gradually increased to only about 25%. In the alloys according to this invention it is desirable that the cobalt content should not exceed 25 particularly when boron is present in proportions of 0.03% or over, as such alloys are difiicult to forge.

To avoid the use of scarce or expensive materials it will be noticed that cobalt and niobium may be omitted and titanium substituted for the latter as in alloy L. 908. The resulting properties are outstanding for so cheap an alloy. Titanium may be avoided in these cobalt-free alloys if niobium is used, for example alloy L. 899.

Having thus described our invention, what we claim as new and desire to secure'by Letters Patent is:

l Alloys comprising:

Molybdenum 0.5-3.5

together with at least one metal selected from the group consisting of niobium, titanium and vanadium, the content of any single element of said group being 05-35%, the total of tungsten, molybdenum and the total content of said group being between 5 and 10%, and the remainder being substantially all iron and incidental impurities.

2. Alloys according to claim 1, containing in addition 22-28% cobalt, the total content of nickel and cobalt not exceeding 3. Alloys comprising the following constituents in substantially the proportions specified: 0.2% carbon, 1% manganese, 0.3% silicon, 25% nickel, 20% chromium, 1% tungsten, 3% molybdenum, 0.03% boron, and 2% titanium, the remainder being substantially all iron and impurities.

4. Alloys comprising the following constituents in substantially the proportions specified: 0.25% carbon, 1% manganese, 0.3% silicon, 15% nickel, 25% cobalt, 20% chromium, 3% tungsten, 3% molybdenum, 0.03% boron, and 1% titanium, the remainder being substantially all iron and impurities.

5. Alloys according to claim 1 which have been subjected to warm working at temperatures between about 500 C. and 900 C.

6. Alloys according to claim 5 which prior to warm working have been subjected to solution heat treatment.

References Cited in the file of this patent UNITED STATES PATENTS 2,432,618 Franks et a1 Dec. 16, 1947 2,432,619 Franks et a1 Dec. 16, 1947 2,590,835 Kirkby et a1. Apr. 1, 1952 

1. ALLOYS COMPRISING MANGANESE 0.5-1.5 NICKEL 13-28 TOGETHER WITH AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISTING OF NIOBIUM, TITANIUM AND VANADIUM, THE CONTENT OF ANY SINGLE ELEMENT OF SAID GROUP BEING 0.5-3.5%, THE TOTAL OF TUNGSTEN, MOLYBDENUM AND THE TOTAL CONTENT OF SAID GROUP BEING BETWEEN 5 AND 10% , AND THE REMAINDER BEING SUBSTANTIALLY ALL IRON AND INCIDENTAL IMPURITIES. 